MCP Ruby SDK Vulnerability: Memory Exhaustion Risk
An early warning has been issued regarding a potential vulnerability in the MCP Ruby SDK that could lead to memory exhaustion and denial of service. Users of the MCP Ruby SDK are advised to monitor for updates and consider implementing workarounds if necessary.
What happened
Reports indicate that the stdio transports in the MCP Ruby SDK may be susceptible to memory exhaustion due to unbounded reading of newline-delimited JSON-RPC frames. This issue arises from the use of `IO#gets` without a limit argument, which can result in uncontrolled memory allocation and potential denial of service.
The vulnerability appears to affect versions of the MCP Ruby SDK, though specific version ranges have not been confirmed. The MCP project has issued several GitHub Security Advisories (GHSA-655Q-2283-6JGJ, GHSA-74GP-QHV5-V493, GHSA-7683-3W9X-CH42, GHSA-WQGC-PWPR-PQ7R) related to this and other potential issues in the SDK.
Professional software engineers using the MCP Ruby SDK are advised to closely monitor the project's GitHub repository for updates and patches. In the interim, implementing a workaround to limit the size of input read by `IO#gets` may help mitigate the risk of memory exhaustion.
How 0Day mitigates this
mcp ruby sdk is anywhere in your dependency tree, the engineers who own the affected repositories get a push alert the moment it is flagged — no manual audit to remember to run.Read how this differs from waiting on a scanner to catch a known advisory, or see the exact, read-only access 0Day needs to do this for an organization.